Wide range tuning circuit



Feb. 6, 1951 PAGE 2,540,137

WIDE RANGE TUNING CIRCUIT Filed Dec. 14, 1945 gwue/wto'v IRVING H. PAGE Patented Feb. 6, 1951 UNITED STATES PATENT -OFFlCE WIDE RANGE TUNING CIRCUIT Irving H. Page, Cheverly, Md.

' Application December 14, 1943, Serial No. 514,245

I 2 Claims. (01'. 250-40) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 O. G. 757) This i'sonantcircuits, and is particularly directed to such .a circuit tunable "over a frequency range broader than can be obtained by conventional circuits, while employing the same range of capacity variation.

It is accordinglyan object of the invention to provide a tunable circuit covering a Wide frequency range through capacity variation.

It is a further object of the invention to provide a parallel circuit tunable over a greatly extended range by simultaneous inductance and capacity variation.

Another object of the invention is to provide a widely tunable circuit for use in applications where it is shunted by fixed capacity.

It is also an object of the invention to provide a tuning circuit by which the effect of fixed shunting capacity is minimized.

The tuned circuit of the present invention is applicable to uses wherein a tuned parallel resonant circuit is shunted by fixed capacity. Manifestly the primary field of utility is in tuned radio circuits of receivers and oscillators. The invention is particularly beneficial when employed in the high frequency region where unavoidable tube interelectrode capacities are of the same order of magnitude as the tuning capacities. For purposes of illustration only, two embodiments shown in the drawing comprise high frequency oscillators.

In the drawings Fig. 1 shows a high frequency oscillator embodying the invention,

Fig. 2 shows the tuning circuit of the invention,

Fig. 3 shows a frequency converter embodying the invention and Fig. 4 shows a tuning unit of the present invention.

The oscillator shown in Fig. 1 includes triode I provided with anode 2, control electrode 3, cathode 4 and heater 5. The tank circuit includes variable capacity 6, and second variable capacity I, the respective elements of the variable capacities being connected by inductances 8 and 9. The inductances are variably coupled. Common control means for operating the capacities and variable coupling inductors may be provided. As will be understood, such control will vary the coupling and the capacity values in the same direction.

Grid 3 is returned to ground through leak Ill, and anode potential is supplied through resistor ll The oscillator frequency is .,-determi.nd by the invention relates to tunable parallel H tank circuit including capacity 1, capacity 6 in parallel with the grid anode capacity of triode l, and inductances 8 and 9, together with the existing mutual inductance.

The tank circuit is shown in Fig. 2. Here it is assumed, for convenience, that the variable capacities are of the same valueC, as are the -inductances L'. M is the mutual inductance. C1 is the fixed shunting capacity. For resonance: I

From which the resonant frequency may be ascertained to be Whereas the specific arrangement shown in Fig. 1 is highly convenient in an oscillator of the type shown, it is apparent from the first equation above that the advantages derive from providing series capacity, part of which is in parallel with the shunting capacity, and part of which is free of shunting capacity, and is not dependent upon the arrangement of the inductance. However, it also appears from the second equation thata simultaneous variation of M with C will provide a further increase in frequency range ratio. By this means a range of 5.5 to 1 may be obtained in the 50 to 500 megacycles per second band.

A frequency converter employing variable inductive coupling is shown in Fig. 3. The oscillator components are the same as in Fig. 1 with the exception that inductors 8 and 9 are mounted for movement relative to each other under control of knob l2, which is also ganged to the variable capacities 6 and I. The incoming signal is supplied to control element 3 through coupling capacity 13 and resistance M from input terminal l5. The output signal is obtained at 59 through transformer I8 coupled to the plate circuit by resistance i6 and capacity ll. It will be understood that such a converter, having a high frequency range coverage of more than 5 to 1, may be employed in monitoring a very broad section of the ultra high frequency spectrum.

The use of the circuit of Fig. 3 permits a simplified physical construction of the variable capacitors and inductances which eliminates all but two sliding contact with attendant elimination of noise generation and inefficiency. Such construction is shown in Fig. 4. Condenser stators 2B and 2| carry interposed fixed inductor 22, while the rotors 23 and 24 are connected by movable inductor 25. The rotatable assembly is controlled by shaft extension 26, rotor 24 being driven by rotor 23 through inductor 25. The system of Figure 4 establishes maximum negative mutual inductance with minimum capacity, and the total inductive and capacitative reactances vary in the same direction with movement of the rotatable assembly. In Fig. 4 the condensers are shown fully meshed and the inductors with minimum coupling.

Such assembly, when incorporated in the circuit of Fig. 3, may have rotor 24 connected to anode 2 and stator 2| connected to grid 3.

The specific embodiments disclosed above do not define the limits of the invention, for which reference to the appended claims may be had.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

Iclaim:

1. A tuning unit for a wide range circuit comprisinga pair of variable condensers each having a fixed element, and a movable element rotatable about an axis, a means positioning said condensers in spaced relationship with the said axes aligned, an inductor connected in driving relationship between the movable elements and positioned asymmetrically with respect to the with, thereby connecting the movable elements,

aligned axes, and fixed inductance means con- 30 nected between the said fixed condenser elements positioned adjacent the aligned axes in variable coupling relationship with the inductor.

2. A tuning unit comprising a mounting memand second inductor means carried by the mounting member in adjustable magnetic coupling to the first inductor means and connected between the fixed elements of the condensers.

IRVING H. PAGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 20 Number Name Date 1,660,108 Vignolo Feb. 21, 1928 1,949,842 Rechnitzer Mar. 6, 1934 1,986,081 Streifi'ert et a1. Jan. 1, 1935 2,011,299 Polin Aug. 13, 1935 25 2,081,711 Polin May 25, 1937 2,106,120 Lindberg Jan. 18, 1938 2,194,696 Eickemeyer et al. Mar. 26, 1940 I 2,272,851 Ramsay Feb. 10, 1942 V FOREIGN PATENTS Number Country Date 388,755 Great Britain Feb. 28, 1933 555,777 Germany Aug. 3, 1932 

